U.S. Pat. No. 4,437,047 discloses a closed loop control system which provides torque command signals to a torque motor that controls the pointing position of the payload platform of a dual-spin satellite. As shown in FIG. 1, the satellite 20 includes a spinning portion 21 and a payload platform 22 having a predetermined line-of-sight 26. The spinning portion 21 includes an infrared earth sensor 25 providing an output pulse when the sensor is viewing the earth. The control system shown in FIGS. 3 and 4 uses the pulses produced by the earth sensor 25 and pulses representing the line-of-sight 26 to provide the torque command signals 57, 58 to control the spinning portion 21.
U.S. Pat. No. 4,143,312 discloses a control system for stabilizing a rotatable antenna mounted on a body to compensate for the pitch and roll of the body. FIG. 1 illustrates the antenna 1 mounted on a platform 3 carried on a deck 4 of a ship by a two-axis gimbal system including a frame 5. The frame 5 is rotatable about a horizontal roll axis 8. The stabilized platform 3 is rotatable about a horizontal pitch axis 9. FIG. 3 depicts a portion of the control system and includes synchro transmitters 10R, 10P to detect relative movement of the antenna 1 about the roll axis 8 and the pitch axis 9. Output from the roll transmitter 10R is applied to a control transformer 11R which also derives an input 17 of roll data from the ship's vertical reference unit (not shown). Based on this data and corresponding pitch data, the positioning of the antenna 1 is stabilized to compensate for the pitch and roll of the ship.
Secondary references are U.S. Pat. Nos. 4,272,045; 4,325,586; 4,355,313; 4,375,878; and 4,418,306.